pcap-log config: sguil-base-dir -> dir and update comment

The code already looks for "dir" first instead of
"squil-base-dir", and already respects this configuration
parameter in other modes than the "sguil" mode.

Coda will still access "sguil-base-dir".

suricata.yaml.in

@@ -341,7 +341,11 @@ outputs:
       max-files: 2000
 
       mode: normal # normal, multi or sguil.
-      #sguil-base-dir: /nsm_data/
+
+      # Directory to place pcap files. If not provided the default log
+      # directory will be used. Required for "sguil" mode.
+      #dir: /nsm_data/
+
       #ts-format: usec # sec or usec second format (default) is filename.sec usec is filename.sec.usec
       use-stream-depth: no #If set to "yes" packets seen after reaching stream inspection depth are ignored. "no" logs all packets
       honor-pass-rules: no # If set to "yes", flows in which a pass rule matched will stopped being logged.